In specific fields of use of catheters or similar devices, for example, electrode lines, a contact pressure against adjacent tissue is significant for the function of the catheter or similar device, such that a measurement of this contact force is of interest. This is applicable, to a particular extent, for what are known as ablation catheters, with which areas of tissue or tissue parts are removed.
An ablation catheter (e.g., “TactiCath” manufactured by Endosense) is known that enables measurement, during an ablation procedure, of the magnitude and direction of a force applied to the distal catheter end—during use that is to say the mentioned contact force. This catheter utilizes the principle of what is known as the FBG (Fiber Bragg Grating) sensor, wherein three fibers, each having an FBG sensor at the fiber end, form the group of sensors required for a 3D force measurement, it being possible to incorporate said sensors for joint measurement signal processing on a signal processing machine. The sensors are attached externally on a deformable cylinder at an angular distance of 120°.
In U.S. Publication No. 2008/0285909, the operating principle of FBG sensors for determining twists or curvatures of the catheter body is described in detail, and the operating mode of the aforementioned force sensor having a plurality of FBG fibers on a deformable cylinder is also explained in this document.
As described in International Publication No. WO 2009/138957, a temperature compensation is provided by means of three electrical thermocouples, because, in the case of the FBG measurement method, even small changes in temperature or deviations between the individual sensors can cause severe measurement uncertainties and, in the case of an electrothermal ablation procedure, rather considerable temperature fluctuations at the tip of the ablation catheter can occur.
The optical measurement principle of the FBG sensor is known in general and, in particular, also in its application for force measurements and temperature measurements; for example see “www.wikipedia.org/wiki/Fiber_Bragg_grating” or A. Othonos, K. Kalli: “Fiber Bragg Gratings: Fundamentals and Applications in Telecommunications and Sensing” Artec House 1999, and (specifically based on voltage measurements and temperature measurements) U.S. Pat. No. 5,399,854. A detailed explanation of the FBG sensor measurement principle is therefore not necessary here.
Irrespective of this measurement principle, other solutions for a contact force measurement on a guide wire or catheter are also known, for example, with use of an optical sensor, as described in International Publication No. WO 2009/007857, or with use of a semiconductor sensor at the tip of a guide wire, as described in International Publication No. WO 2008/003307.
More recent improvements to the aforementioned solutions are the subject of U.S. Publication No. 2012/0220879 and U.S. Application No. 61/703,272, also in the name of the Applicant herein.
The present invention is directed toward overcoming one or more problems associated with current catheters.